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Method and apparatus for processing low resolution images of degraded bar code symbols

  • US 5,276,315 A
  • Filed: 05/14/1992
  • Issued: 01/04/1994
  • Est. Priority Date: 05/14/1992
  • Status: Expired due to Term
First Claim
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1. A method for decoding a bar code symbol oriented in a bar direction from a two dimensional digital input image representative of said bar code symbol, said two dimensional input image being comprised of gray scale pixel values received from a CCD sensor, said bar code symbol being comprised of a plurality of modules each of which has at least one bar and at least one space, wherein information is encoded in each of said modules in accordance with its width, comprising the steps of:

  • (A) dividing said two dimensional input image into a plurality of non-overlapping two dimensional sections, each of said two dimensional sections being bounded by first and second reference lines substantially parallel to said bar direction and third and fourth reference lines substantially perpendicular to said bar direction, wherein said third and fourth reference lines are spaced at least two pixels apart, and wherein said first, second, third and fourth reference lines are oriented omnidirectionally with respect to the rows and columns of pixels in said input image;

    (B) determining a plurality of intensity information values representative of the intensities of corresponding sections of said plurality of sections by summing pixel values derived from said input image lying in each of said sections;

    (C) forming a one dimensional intensity projection signal by arranging said plurality of intensity information values along an axis, said one dimensional intensity projection signal having a plurality of corresponding peaks;

    (D) calculating the areas of a plurality of regions described by said one dimensional intensity projection signal, wherein each of said areas is bounded by a portion of said one dimensional intensity projection signal and said axis, said portion lying between corresponding peaks of said one dimensional projection signal; and

    (E) determining the widths of a plurality of bars in said bar code symbol from said areas.

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